Speaking-machine.



No. 881,546. PATBlxrTED MAR. 10,1908.

' G.L.cHIsHoLM.

SPEAKING MACHINE.

yAPPLIUATION FILED JAN. 5, 1907.

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A A fr0/ws Ys A support `the diaphragm so that its surfaces CHARLES L. QHISHOLM, OF MARYSVILLE, NEW BRUNSWICK, CANADA.

SPEAKING-MACHINE.

Specification of Letters Patent.

Patented March 10, 1908.

Application filed January 5, 190'1.A Serial No. 350,979.

T o all whom it may concern:

Be it .known that I, CHARLES CHIsHoLM,

a subject of the King of En land, residing at Marysville, New Brunswick, Canada, have invented a new. and useful Speaking-Machine, of which the following is a specification.

The invention relatesto acoustic'instru- .ments, and particularly to recorders and reproducers for phonographs and similar ma# chines, and the object in view isto provide a construction andarrangement of dlaphragm and stylus whereby the sound waves or beats affect the diaphragm on truly concentric lines and the stylus receives an accurate vibration in accordance lwith the A sound or sounds attacking the diaphragm toA avoid the 4formation of secondary or false vibrations due to obstacles in the way of a true and accurate and free vibration of the diaphragm, and thus avoid the formation of such a record as in reproduction will result in secondary or false tones or harmonics. To accomplish this-it has beenfound necessaryin the first place, as more fully explained hereinafter, to

are entirely unobstructed and are freel to vibrate and to receive the true `wave beats of sound without interference, and to construct .sensitive diaphragm ordinarily employed in machines of thistype and made'necessary by the fact that the attachment of the stylus is f accomplished by wings or disks which obstruct and prevent the vibration of the central portion of the diaphragm, and, also, by the attachment of tue stylus arm tothe sur- 'face of the diaphragm from the central point to the periphery thereof, that not only are the vibrations of the diaphra m broken and interfered with but the secon ary or reduced vibrations owing to this flexibility or sensitiveness,` produce false tones and harmonics, andthe real over tones which are necessary to 'give character tothe fundamental tones reaching the diaphragm are lost v or are dis-` posed opposition to each other, so as to be-- 'usually V icliaiiifgv ed character or nullified.

leavin the diaphragm entirely unobstructed from t iis central point, whichas above indicated, is of practically no appreciable area to its periphery, a very much thicker and more rigid diaphragm can be employed, and that the over tones can be reproduced and the vibrations accurately and truthfully conveyed to the record so as to be subsequently reproduced. 1

In addition to the foregoing it has been found that the necessary intimate relation or true contact of the stylus with the center point of the diaphragm can be eHected without securing the point of the stylus arm to the diaphragm at such central point, and thatv oint upon the center vof the diaphragm can e varied to produce greater or less tension, and with these andother objects, which will .alppear as theifvention is more fully discosed, the invention consists in' a certain construction, combination and arrangement of parts which will be Ahereinafter disclosed, it being understood that various changes in the form, proportion, and minor d etails of' construction may be made without departing from the spirit of the invention, whlch is set forth in the appended claims.

In the accompanying drawings :Figure 1 is a sectional view of a recorder constructed in accordance with the invention. Fig. 2 is a face view of the same. Fig. 3 is a detail l Therefore, it has been further found that by l view showing the means for adjusting the spring tension. Figs. 4, 5 and 6 are diagrams of diaphragms showing sound wave formac tions.

Similar reference characters represent corthis diaphragm upon its support, or, in other words, at the dea dor non-vibratory lportion of the diaphragm. The stylus arm is of yielding Vspring quality, having a spring tendency toward the diaphragm with its contact point 5 reduced to bear upon the geometrical center of the diaphragm with the minimum area of contact. y

ln order that the tension of the stylus arm, or the spring tendency thereof toward the diaphragm may be. varied, a spring bearing arm 6 is employed, being supported at its outer end at the non-vibratory periphery of theI diaphragm, and being adjustable by any suitable means, such as a cam 7, so as to ex# ert a greater or less. pressure vupon the stylus arm with which it contacts, or over which it extends, and upon which it has a bearing, as indicated in the drawings.

By giving the stylus arm, which at itsattached outer end is -in a plane substantially parallel with the surface of the diaphragm, an upward sweeping curve, it is possible to position the stylus point at the desired angle with reference to the plane of the surface of the diaphragm, and hence, to the surface of the record or blank, so as to produce the best results, while the bearing point of the arm starting back of the point of the graver or stylus point, extends forward and has its bearing upon the exact center of the .diae phragm, and directlybeneath the extremity of the stylus point. This insures the accurate transmission of motion of the center of the diaphragm to the stylus point, and hence insures 'an accurate record. lt has been found in practice that the relativelyT thick or heavy diaphragm instead of being less sensitive to sound waves is more sensitive than the disks of smaller gage or less thickness, owing to the entirely -nnobstructcd areas thereof, there being no attachment of any kind at any point on the surface of the diaphragm Within the area of its peripheral support, and the only object in contact with any portion of the surfaceof the diaphragm being the bearing point of the stylus which, as above indicated, is made of almost unappreciable area. The effect of this construction lis that the diaphragm, while responsive, to

themost sensitive sound waves, does vnot prolong those waves and thusset up secondary or false vibrations which result in a false' record. The rigidity of the diaphragm is such that having received an impulse due'to an impinging sound wave, it truthfully answers to the impulse and then returns toits normal position. lt has been found that whispers can be accurately recorded and as truthfully reproduced while concerted or orchestra work can be produced with accuracy and without. the confusion due to harmonies, all of the more sensitive over vtones being accurately recorded, and as accurately reproduced..

InFig. 4 has been shown a diagram of a l diaphra m in which the stylus arm 1s secured on a ra lal line extending from the center to the periphery. vand indicating by the dark broken lines the broken 4beats resulting .from

a nodal condition due to the hiet, that the arm acts as a damper and interferes wil h the vibrations of that portion of the diaphragm. ln that event the.,undan 1pered portion or half is not free to vibrate as when the diaphragm is entirely unsupported, for the reason that the condition of the dampered portion of the diaphragm serves to obstruct the movement of all parts of the diaphrann.

ln Fig. 5 is shown a diagram indicatng the effect of covering'a portion ol' the surface ot' the disk at its center with an attaching device for the stylus, and indicating that not. only is theportion of the disk thus covered rendered inert and dead. so far as sound production is concerned, but the effect thereof is that of a damper to interfere with the proper formation of the waves in the surrounding vportion of the diaphragm.

y Fig. 6 illustrates a diaphragm free to vibrate under normal conditions wherein the wave lines are perfectly concentric and extend from the center to the periphery of the dia hragm. claim:-.-

1. In a device of the class described; a rigid, peri herally supported and otherwise superficial y unobstructed diaphragm, and a stylus having a bearing upon the center of the diaphragm cireumscribed in area to substantially that of a geometric point, said diaphragm being of such thickness as to be undeflected to any appreciable extent from its normal diamctric plane. by the pressure neeessary to maintain the bearing point of the stylus in constant contact with the diaphragm'.

2. In a le\'i eof the class described; a rigid, peripherall)- supported and otherwise superlieiallv unobstructed diaphragm, and a stylus in yielding contact but unattached to the center of the diaphragm, with the bearing circumseribed in area tothut ot' a getunetric point, the said diapluagni being ol a thickness to resist dellection by the pressure necessary to maintain the stylus in unbroken contact with the diaphragm.

ln a deriee of the class described; a rlgid, peripherally supported and otherwise snperfieially unobstructed diaphragm; a stylus bearing upon the center of the diauvihragni with the area of contact eircumscribed to substantially that of a geometrie point, the said diaphragm being of a thickness to resist i deflection by the pressure. necessary to maintain the stylus in unbroken contact with the diaphragm, and a spring arm cooperating wlth the stylus to establish a ylcldnlg-contact .between the stylus -bearing point 4and the diaphragm.

4. In a device of the class described; a peripherally supported and otherwise supericially unobstructed diaphragm, and a sty- 'lus in constant contact with but unattached yte the diaphragm at its center, with the area Cil Y ripherally supported of contact circumscribed to substantially p that of a geometric point.

5. In a device of the class described; a pe-l ripherally supported and otherwise su er' cially unobstructed diaphragm; a sty us, and a bearing for the latter in constant conp at its center, said bearing being attached to t the stylus back of the'styluspoint and hav' ing its point of contact with the diaphragm in a'plane cutting the center of the latter and the graving point of the stylus, and the area l' of contact between the bear-ing point and the diaphragm closely approaching a geometric oint. v Y *i p 6. In a device of the class described; a peand otherwise superficially unobstructed arm having its supporting end substantially having lts contact wit'ht center thereof and of an 'area closely apmy own, K 1n the presence of two witnesses.

diaphragm; a stylus l arallel with the surface of the diaphragm and curved away therefrom toward its graving point, and

a bearin for the stylus arm Ile diaphragm at the roaching a geometric point, the said bearing and its supporting In testimony that I claim the foregoing as I have hereto affixed my slgnature CHARLES L. CHISHOLM.

- 25 tact with but unattached to the diaphragm being connected to the 'stylus arm between he graving end thereof end and lying in'a plane cutting the center of thediaphragm and the graving point of the stylus. 

